People need to be well enough to administer the fatal dose, but many seriously ill people just can't physically do this. It really highlights the cases which have just gone to the High Court today, where severely disabled people want the right to have their lives ended by a doctor, without the doctor being accused of murder.
There was the recent case of Tony Nicklinson, where the court rejected his request. It was horrible to hear his screams / moans when the verdict was delivered. He died not long after, I suspect he starved himself. There didn't seem to be a lot of care, consideration or respect for him.